Physical uplink control channel procedures are discussed in Release 10 of the 3GPP Long Term Evolution (LTE) standard, as described in 3GPP Technical Specification No. 36.213 version 10.1.0 Release 10, “Physical layer procedures.” Coordinated multi-point (CoMP) transmission and reception have been considered for LTE-Advanced as a way to improve the coverage of high data rates, to improve cell-edge throughput, and to increase system throughput.
When only a primary serving cell transmits physical downlink shared channel data to a user equipment configured with multiple serving cells, the user equipment transmits the corresponding hybrid automatic repeat request and acknowledgment (HARQ-ACK) using physical uplink control channel format 1a/1b. When a secondary serving cell transmits physical downlink shared channel data to the user equipment, the user equipment transmits the corresponding HARQ-ACK using physical uplink control channel format 3.